refactor: standardize variable naming and file formatting

- Rename Quantity to quantity in BomItem for consistent naming convention
- Update references in MainModule to use lowercase quantity
- Add newlines at end of files for consistency
- Update vba_metadata.json with new source path and document module

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

VBA/vba_metadata.json

@@ -1,6 +1,12 @@
 {
-  "source_file": "C:\\Users\\pengq\\Downloads\\AutoBOM\\AutoBOM\\YTHN-100_-_Claude3.xlsm",
+  "source_file": "C:\\Users\\Administrator\\Desktop\\新BOM\\AutoBOM\\YTHN-100.xlsm",
   "modules": {
+    "Sheet9.cls": {
+      "name": "Sheet9",
+      "type": "DocumentModules",
+      "attributes": {},
+      "file": "DocumentModules\\Sheet9.cls"
+    },
     "MainModule.bas": {
       "name": "MainModule",
       "type": "Modules",